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Global climate change is increasing the range of temperatures that crop plants must face during their life cycle, giving negative effects to yields. In this changing scenario, understanding the genetic control of plant responses to a range of increasing temperature conditions is a prerequisite to developing cultivars with increased resilience. The current work reports the identification of Quantitative Trait Loci (QTL) involved in reproductive traits affected by temperature, such as the flower number (FLN) and fruit number (FRN) per truss and percentage of fruit set (FRS), stigma exsertion (SE), pollen viability (PV) and the incidence of the physiological disorder tipburn (TB).These traits were investigated in 168 Recombinant Inbred Lines (RIL) and 52 Introgression Lines (IL) derived from the cross between Solanum lycopersicum var. "MoneyMaker" and S. pimpinellifolium accession TO-937. Mapping populations were cultivated under increased temperature regimen conditions: T1 (25 • C day/21 • C night), T2 (30 • C day/25 • C night) and T3 (35 • C day/30 • C night). The increase in temperature drastically affected several reproductive traits, for example, FRS in Moneymaker was reduced between 75 and 87% at T2 and T3 when compared to T1, while several RILs showed a reduction of less than 50%. QTL analysis allowed the identification of genomic regions affecting these traits at different temperatures regimens. A total of 22 QTLs involved in reproductive traits at different temperatures were identified by multi-environmental QTL analysis and eight involved in pollen viability traits. Most QTLs were temperature specific, except QTLs on chromosomes 1, 2, 4, 6, and 12. Moreover, a QTL located in chromosome 7 was identified for low incidence of TP in the RIL population, which was confirmed in ILs with introgressions on chromosome 7. Furthermore, ILs with introgressions in chromosomes 1 and 12 had good FRN and FRS in T3 in replicated trials. These results represent a catalog of QTLs and pre-breeding materials that could be used as the starting point for deciphering the genetic control of the genetic response of reproductive traits at different temperatures and paving the road for developing new cultivars adapted to climate change.

Water is an essential resource for food production, as agriculture consumes close to 70% of the 15 total freshwater, and its shortage is becoming critical in arid and semiarid areas of the world. 16 Therefore, it is important to use water more efficiently. The objectives of this project are to 17 determine the productive response and the irrigation water use efficiency of seedless watermelon to 18 three irrigation management strategies over two growing seasons. This was done by applying 100, 19 75 and 50% of the irrigation water requirements (IWR) the first year, in the second year added six 20 additional treatments, of which three treatments were regulated deficit irrigation with 75% IWR 21 during the vegetative growth, fruit development and fruit ripening stages, and the other three 22 treatments were with 50% IWR during the same stages. The exposure of watermelon plants to 23 severe deficit irrigation resulted in a reduction in dry biomass, total and marketable yield, average 24 fruit weight, fruit number and harvest index, and without improvement of marketable fruit quality. 25 The fruit ripening was the less sensitive stage to water deficits. Relative water content and cell 26 membrane stability index decreased as the water deficit increased. Irrigation water use efficiency 27 decreased to a lesser extend during the fruit ripening stage than when water restriction were 28 applied during different growth stages. If water is readily available, irrigating with 100% of water 29 requirements is recommended, but in the case of water scarcity, applying water shortage during fruit ripening stage would be advisable.

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Background Due to global warming, the search for new sources for heat tolerance and the identification of genes involved in this process has become an important challenge as of today. The main objective of the current research was to verify whether the heat tolerance determined in controlled greenhouse experiments could be a good predictor of the agronomic performance in field cultivation under climatic high temperature stress. Results Tomato accessions were grown in greenhouse under three temperature regimes: control (T1), moderate (T2) and extreme heat stress (T3). Reproductive traits (flower and fruit number and fruit set) were used to define heat tolerance. In a first screening, heat tolerance was evaluated in 219 tomato accessions. A total of 51 accessions were identified as being potentially heat tolerant. Among those, 28 accessions, together with 10 accessions from Italy (7) and Bulgaria (3), selected for their heat tolerance in the field in parallel experiments, were re-evaluated at three temperature treatments. Sixteen tomato accessions showed a significant heat tolerance at T3, including five wild species, two traditional cultivars and four commercial varieties, one accession from Bulgaria and four from Italy. The 15 most promising accessions for heat tolerance were assayed in field trials in Italy and Bulgaria, confirming the good performance of most of them at high temperatures. Finally, a differential gene expression analysis in pre-anthesis (ovary) and post-anthesis (developing fruit) under heat stress among pairs of contrasting genotypes (tolerant and sensitive from traditional and modern groups) showed that the major differential responses were produced in post-anthesis fruit. The response of the sensitive genotypes included the induction of HSP genes, whereas the tolerant genotype response included the induction of genes involved in the regulation of hormones or enzymes such as abscisic acid and transferases. Conclusions The high temperature tolerance of fifteen tomato accessions observed in controlled greenhouse experiments were confirmed in agronomic field experiments providing new sources of heat tolerance that could be incorporated into breeding programs. A DEG analysis showed the complex response of tomato to heat and deciphered the different mechanisms activated in sensitive and tolerant tomato accessions under heat stress.